Oil purification



Sept. s, 1925.

L. H. CLARK OIL PURIFICATION Filed Nov.

INV NToR ATTORNEY Patented Sept'. 8, 19252.

"Unire LEE H. CLARK, OFROSEMONT, PENNSYLVANIA, ASSIGNO'BIO THE SHARPLES SPIEL CIALTY COMPANY, F PHILADELPHIA, PENNSYLVANIA, A CORPORATION 0F DELA- WARE.

OIL PURIFICATION.

Application mea November'zs, 1924. serial No. 752,874.

To all whom t may' concern: o Be it known that I, LEE H. CLARK', a citizen of the United States` residing in Rose- .w to which they have been put, of decomposition products, free fatty acids, and colloidally suspended substances orl one orl more of such or other impurities.

l An object of my invention is to provide a method and apparatus whereby oil may be prepared or restored or renovated and so brought to a condition` wherein it is We adlpted to a particular use. ixamples of oils in which impurities have been produced by reason ofC or'during their use and which may be purified in accordance with my invention are oils that have been used toA immerse electric switches, cirlcuit breakers and transformer coils which carbon in colloidal form has been produced during their -normal use and which may lalso contain water, soaps of vheavy metals, decomposition products, and other impurities, and the acidity of which is increased during their use. Another eX- ample of such oil areoils that have been used for the lubrication of internaly combustion engines and contain suspended carbon, organic acids, other decomposition products and other impurities.

A. further but important object of the ypurification that is to be accomplished by the'use and practice of my invention is the removal of impurities that lessen the resista'nce ofthe oil to emulsilication. The

complete purification or renovation or restoration of oil that is to be used to immerse circuit'breakers in electric circuits of high potential will ordinarilyfinvolve the removal of the impurities -abo've mentioned` and also such impurities as lessen the re- Y sista-nce of the oil to emulsitication. However, it may be desirable in some cases to merely remove the impurities previously mentioned without regard to the ultimate abilityof' the oil to resist emulsification.

.Other oils than those specifically mentloned and into which similar impurities have been introduced by reason of or during the use to which the oils have been put, or otherwise, may he purified or restored in accordance with my invention, and although purification of oil in 'accordance with my .invention may neutralize or otherwise remove tlre acidity of the oil such removal of acidity 1s incldental to the process, and m invention is notv to be confused with the mere' neutralization of sour oils that are produced in the course of acidV purification.

Other and further objects of my invention will appear from the following description.

'In purifying, in accordance with my invention, oil that contains or in which one or more of the above mentionedl impurities have been produced during the use thereof,

Vthe oil is treated with an aqueous solution or reagent that has the property of being dispersed more easily than pure water throughout the oil and. thel property of causing impurities to be removed from the oil? as by passing into the aqueous phase of the mixture that comprises oil' and dispersed aqueous reagent or by being put into a state wherein their removal may be effected by treatment in accordance with 'my invention. A dispersion of such reagent throughout the oil may be advantageously effected by agitation of sufficient violence and duration to cause the aqueous reagent or phase to be carried to all parts of the mixture in small particles or globules in order that some of the aqueous reagent or phase will lie closely adjacent to`but notl necessarily in contact with every .part of the oil that is to be purified. 'The mixture is advantageously maintained in a heated state during agitation by heating one or both of the constituents thereof prior lto their admixture or by heating the. mixture or by any one or more of such expedients. The temperature to which the mixture is brought-is dependent upon the viscosity of the oil that-is being treated and should be sufficient to insure that agitation will produce such dispersion of the reagent within the oil as will b ring it into close relation with the impurities, ,and sufficient to rrender after more fully set forth. The mixing oil and the aqueous reagent that provides effective the subsequent treatment, for 'example, treatment in centrifugal machlnes.

The aqueous`reagent should be sufficient inl quantity and strength to satisfy the ainities of the impurities in the oil and still provide a sufficientexoess of active reagent to insure that the reagent will be properly dispersed throughout the oil and will cause the impurities to be removed from theoil as b passing into the aqueous phase of the resulting mixture. The relative quantity of aqueous solution or reagent or phase that 1s agitated with the oil to be purified may vary 'in the treatment of different oils and oils containing.y different impurities as herein the aqueous phase ofthe resulting mixture may be carried' on continuously or the mixture may be produced in batches,

After the aqueous reagent is properl dispersed throughoutfthe 011 to be purili such treatment of the mixture as will cause a separationtherefrom of the ueous phase thereof results in purification o the oil, impurities being carried 'out with the aqueous i phase or put into a state in which the oil may be freed ofvthem by treatment of the oil in accordance with my invention. In order to advance the degree of purification -of thev oil and also to improveits resistance to emulsification a particular reagent is em ployed under some circumstances and under out previous treatment of the oil in accord-i ance with my inyention. o

The aqueousl reagent or aqueous phase of the mixture that is formed with the oil may be prepared 'by dissolving in water substances that impart to the reagent the property of dispersing more easily than pure water throughout the oil and render it effective to separateimpurities therefrom. Such substances'include alkaline substances such as caustic soda, soda ash, tri-sodium phosphate and other alkaline substances that produce the desired effects while Iin solution.

If the' reagent is prepared from lan alkaline substance the degree of alkalinity of the reagent must "be such as to render the reagent capable of being more easily dispersed in the oil than is pure water and capable of causing removal of the impurities therefrom.

However, excessive alkalinity of the resultmixture is to avoided because of the 'danger of preventing soapsalready present in the oil or that may be formed with the fatty acid present from dissolving in the aqlleous phase and thereby rendering the oil su ject to emulsification, sludging, etc. In

the practice of my invention in connection with the purification of impure oils containing finely divided carbon, some of which may be in colloidal form, such as switch oil .and transformer oil and lubricating oil of internal'combustion engines, I have successfully employed a reagent having an available, though not in every case initially free,

soy

caustic soda having been found generally applicable an work.

I have found that in the purification of oil in accordance with my invention advantage may be gained-by the use of a reagent of which at least some part of the substance present is in colloidal suspension or solution. An effective solution of'such character may be produced by the use of sodium silicate, particularly sodium silicate in which silica predominates by weight, for example, in which there are 3.25 arts byfweighteof SiO2 to each part of Na2 or sodium aluminate or any reagent that gives sufiicient alkaline concentration and in addition gives naturally, or can be made to give by' combination with other agents, the required colloidal conc'pnvenient for commercial ditions. The required colloidal condition is v attainable bv introducing into the reagent very finely divided silica which is a crystalline substance in its dry state, or by introducing into or producing in the reagent an extremely soft and gelatine-like colloidsuch as aluminum hydroxide, the colloid produced by sodium silicate being relatively firm as e compared with aluminum hydroxide. It is possible, though I do not desire to be bound by such theory, that the colloidal substance enmeshes solid or semi-solid or colloidal impurities, including carbon particles that have .been wetted bv the solution, but which by reason of attached oil have a specific gravity between that of oil and water, and causes them`to separate readily from the oil. I have found that by the use of a colloidal reagent the layer of sludge that ordinarily forms between the oil and the murky alkaline watelr does not occur but on the contrary 4there is produced a sharp line of separation between the oil and murky water and the solids or semi-solids that otherwise form a sludge line between the oil and water will 'sink in the wafer. rRecovery of pure oil is facilitated by causing the impurities that would, otherwise float, at '-.the linterface between the oil and aqueousphase to sink. in

the aqueous phase.

'Ireatmentof impure oil with a reagent of the character and in themanner above deoil that is discharged from the' centrifugal1 separator appears to have been sufficiently purified so that by further treatment, in accordance with my invention as herein described, it is rendered suitable for re-use, it indicates that the proportion of water in the emulsion has been correct and that the alka line concentration has been correct, but if the oil does not appear to be sufficiently purified this is an indicationthat the conditions of the aqueous phase of the emulsion were incorrect for the particular oil treated.A

Thus, if the oil appears to be insufficiently purified and the aqueous discharge from the centrifugal separator is turbid but light in shade lthe degree of alkalinity of the aqueous alkaline reagent used was insufficient to effect a substantial removal of the impurities, ye. g. colloidal carbon, contained in the oil being treated. On the other hand if theaqueous discharge from the centrifugal separator contains a high -concentration of removed impurities and the oil appears to have' been insufficiently purified this indicates that'the mixture produced by lthe agitation contained an insufiicientrproportion of the aqueous phase.

If, in the treatment so far described,a reagent including a colloidal component has been used, it will be found that the resistance of the oil to emulsibility has been improved if the resistance to emulsibility of the original impure oil was very unsatisfactory.

In order to make as full a disclosure'of my invention as possible but' with the express understanding that I am not bound thereby it is my beliefthat the removal of impurities' in accordance with my invention is effected by electric action. The aqueous -solution or reagent or phase contains'a substance that imparts to it the property of widely and easily dispersing within the oil, pferhaps as'discontinuous particles, the oil ing continuous, and it is my present belief that the reagent vso dispersed contains and carries throughout the oil negative charges adsorbed at the-oil-water interface and lthat impurities including carbon particles being positively charged are thereby attracted to -and caused to concentrate at thatinterface and that the positive charges are neutralized and flocculation of the impurities occurs andI the preferential wetting of carbon by the aqueous phase permits as Well as causes the carbon particles to pass into thev aqueous phase. In other words the negative charges carried throughout the oil by the aqueous phase cause impurities to pass to and into the aqueous phase whereby they are removed by it or s'uch charges otherwise put the impurities into such state that they may pass out with the aqueous phase particularly when that phase is separated from the mixture by meansof a centrifugal device. The mere ability of a substance to wet the carbon particles is apparently not sufficient to cause them to pass vreadily into the aqueous phase and it is apparently essential to the attainment of a high degree of purification that the aqueous phase contain a substance that will attract to itself from the oil electrically charged impurities of the oil; A substance that merely wets the carbon particles must be brought into actual contact with each carlbon particle vbefore such wetting can occur.

With the substances that Iy describe the particles will migrate tothe dispersed reagent because of the opposite charges present. My belief that this theory explains the effectiveness of my invention is supported by the'fact that a soap solution is known to wet carbon but to remove carbon'particles from oil it is necessary mechanically to bring such soap solution into actual contact with each individual particle whereas the substances employed in accordance with my invention need only be sufficiently dispersed within the oill to permit the impurities of the oil to be drawn within themhasfby beingcaused to concentrate at the interface and to be subsequently preferentiallyavetted. In substantiation of the fact that\clectrically charged impurities of the oil are attracted to globules of a reagent that produce an op-posite charge at the interface between the reagentand the oil, it has been demonstrated thatfinely divided carbon. particles existing as an impurity in oil are positively charged and it is well known that globules of aqueous reagent dispersed in oil are rendered negative at"the oil-water interface by the presence in the globules of hydroxyl ions that are due to or freed within the reagent by thepresence in the reagent of an alkaline or other substance that will produce in water free hydroxyl.

ions. r

I'f treatment of the impure oil by the steps so far described has not satisfactorily purified the oil'or rendered its resistance to emulsification satisfactory, fullers earth Bor other decolorizing clays or any similarly adsorptive material may be added to the oil at this stage. I have found thatin treating oil at this stage b y the use of such adsor tive material only an amount of the order o one quarter of one percent need be added whereas I have found it impossible to obtain sufficient purification by the use of even very large amounts of adsorptive material if the alkaline treatment of the oil is omitted.. Treatment in accordance with my invention puts the oil in such condition that very small amounts of adsorptive material' will enhance the purity thereof and effect that purification or alteration of the oil whereby its resistance to emulsification is made satisfactory. It is possible that treatment by caustic soda or other non-colloidal reagents will not improve the resistance to emulsification of oils that were'not originally particularly bad in that respect but the resistance to emulsification of such oils may be made entirely satisfactory by the use of such small amounts of adsorptive material. If the original impure oil is very poor in respect to its resistance to emulsification, its resistance to emulsification is improved by the use of a reagent containing a colloidal component and made entirely satisfactory by further treatment with such small percentage of adsorptive material; and such small percentage of adsorptive material will make fairly satisfactory the resistance of oil of poor resistance to e1nulsification that has been treated with a non-co1- loidal .alkaline reagent. v

At this stage oil that has been mixed with a Suitable reagent and from which the aqueous phase of such mixture has been removed, preferably by a centrifugal separator, is now advantageously treated in a centrifugal clarifier regardless of whether or not it has been treated in the meantime by any adsorptive material. Such treatment will remove any residual water as well as other impurities and will, if adsorptive material has been added, remove that material together with impurities that have been adsorbed by it. In the treatment of certain oils the quality of the oil discharged from the clarifier may be improved by delaying its introduction into the clarifier after it has been discharged from a centrifugal separator. The adsorptive material may be introduced in any manner so long as it is introduced in a uniform proportion. In accordance with my invention oils contaminated as abovedescribed may be purified and put into condition for re-use for the purposes in which they became contaminated, although the contaminating impurities therein are of such a character that the oils cannot be practicably purified by methods heretofore known, e. g. by the use of previously known centrifugal processes or filtering devices such as blotter filters, and

' if desired the resistance of the oil to emulsi 'which it became contaminated, the cost of such restorationbeing but a small percentage of the value of the oil.

As a specific example of the purification of oil in accordance with my invention, I herein describe the purification of oil that has been used to immerse electric circuit breakers or switches, with the understanding, however, that my invention is not limited to that specific application.

Oil that had been so used and that had a viscosity of 100 seconds Saybolt universal viscosity atI 100 F. and which contained a .substantial proportion of suspended colloidal carbon, moisture, and other impurities and which could not be purified or restored practicably. by processes heretofore known, e. g., filtration through blotting paper, or ordinary centrifugal treatment, was mixed with an aqueous solution of caustic soda, nine parts of contaminated oil being mixed with one part of aqueous alkaline agent, the aqueous alkaline agent containing one half of one percent of caustic soda. And, similar oil was treated by an aqueous solution of sodium silicate of which the proportions of Na. .O and SiO2 were as above set forth in which the sodium silicate amounted to 2% by weight of the aqueous solution or reagent. In each case. the `mixture was maintained at a temperature of 170 F. and violently mechanically agitated for about three minutes. This agitation produced a turbid emulsion, and the mixture so produced was flowed through the bowl of a centrifugal separator, generally of the type above mentioned, the agitation of the emul sion being continued and the temperature thereof being maintained during the time that it was flowing to the centrifugal bowl. The aqueous discharge from the centrifugal separator consisting ofthe aqueous phase of the mixture was turbid and had a grayish through a centrifugal clarifier at the same ratc at which it was discharging from the centrifugal separator. The oil discharged from the clarifier and which had first been treated with caustic soda was substantially free of moisture, colloidal carbon and other impurities, was light in color. The samples ofoil that were treated with sodium silicate were purified in the respects above specified and it appeared that there was an advantage gained in using such. colloidal .reagent.I

Wivth samples of switchvl that were very trifugal separator and the oil was thenrimani of switch oil having fair lresistance to emulsification that had been treated with caustic soda as Well as samples of oil having poor resistance to emulsification that had beenA treated with sodium `silicate were treated with fullers earth by adding onequarter of one per cent by Weight of fullers earth that had previously been mixed with oil to assist in dispersing it through the oil to be treated. .The fullers earth was added to the oil after it had passed through the cenpassed through a clarifier which removed the f ullers earth and any traces of moisture and other impurities that .were in the oil after it passed through the separator. The oil discharged from the clarifier was substantially free of moisture, colloidal carbon and other impurities, was light in color and had an entirely satisfactory resistance to emulsificatiom and was' ready for re-use.

I have found that treatment of such impure oil in the manner above described makes it possible to employ centrifugal machines in the purification thereof but I do not intend that my invention shall be limited to the use of centrifugal machines as my invention embraces the purification of such impure oil by the use of the reagents and materials and steps above specified regardless of what devices are employed to effect v the separations that are eected in the separator and clarifier in the example above described. v

` l If the oil treated in accordance with my invention is of such a character that the oil discharged fromu the centrifugal separator possesses the properties that are desirable in connection with the particular use that is to` be made of the oil it iseapparent that the Yclarifier need not be used. While certain oils contaminated as above described may` -be so handled during their treatment in the of oil discharged from the separator. Thus,

under certain conditions, an attempt to produce the desired degree of purication of the `oil without using a clar1fier would tend toward an ineflicient utilization of the separator as by requiring a disadvantageously reduced capacity thereof, whereas operation of the separator at usual or rated capacity will purify the oilto a sufficient extent to make it possible to restore the oil to a condition in which it is suitable for re-use by passing it-through a clarifier in accordance with my invention.

In order to assist inthe understanding of my invention but with the understanding that my invention is notlimited thereto I describe herein and show in the drawings accompan ing this specification apparatus whereby t eprocess above specifically described may be carried out.

In the single figure of the drawings I have' showndiagrammatically one form of apparatus Whereb one application of my invention may be gsactised.

In the drawings the agitating tank 1 may be continuously or intermittently fed with the oil that is to be purifiedby means of the pump 2 and the feed pipe 3, and it may be similarly fed with an aqueous alkaline reagent, for example, caustic soda, b means of the pump 4 and feed pipe 5. hen the proportion of aqueous alkaline reagent to oil has been determined the pumps 2 and 4 i may be connectedfor simultaneous operav tion to produce a continuous'orintecrmittent supply of oil and alkaline in the desired proportions. If the oil'and aqueousv alkaline has notbeen previously heated the mixture thereof may be heated in the agitating tank l by a steam or electric coil 6 andv the mixture may be agitated in any' manner, for example, by means of the agitating wheels 7 that are driven in any desired way by means of the shaft. 8 and which may advantageously lie on opposite sides of the baiiie plate v8 The agitator is driven at suiicient speed to produce agitation suiiiciently violent to bring the aqueous alkaline into contact with the impurities of the oil or into proximity therewith.l While the mixture is maintained at the desired temperature and the agitation is y preferably being continued 4the resulting mixture is-led by the pipe 9 to the centrifugal separator 10 and the aqueous. hase of. the mixture 'is discharged through t e spout purified. Oil is discharged from the centrifugal separatorlO through the spout 12 into the .receiving tank 13 from which. it is 11 and contains impurities of the oil being f' passed throu h pipe 14. by means of the pum 14: to t e centrifugal clarifier 15 fromV -whic it is, discharged in a condition in which it may be re-used. The fullers earth or other adsorptive material is ladded `to the oil before it is introduced into the clarifier as by introducing it into the oil in the tank A13 by any suitable device suchas the pipe 13. If ity isdesired to dela. the introduction to the clarifier 15 of the oildischarged from the separator 10 the lpipe 14 may-be provided with a by-pass 16 around the pump 14 and having a valve 16 controlled by a oat 17 in the receiving tank 13 in any a propriate manner, for example, by means o the lever 18 pivoted, at 18. By adjustment of the position of the lloat 17, for example, by screwing it up or down upon the guided rod- 19 on which it is threaded, the amount of oil that v must be in the tank 13 before any oil will flow to the clarifier 15 may be regulated. It will be apparent that the valve 9 in the pipe leading to 'the centrifugal separator may readily be controlled in Vconnection with the valve 16 in order to properly regulate the rate of How of the mixture through the apparatus employed.

From the foregoing it will be apparent that I herein describe a process and apparatus whereby it islpossible to remove from oil impurities that are difficult to remove and wherebysuch purification of oil as may be eli'ected by the use of alkaline reagents can be carried out and whereby the oil containing one or more of the impurities above mentioned may be sufficiently uried to render itcapable of beifig re-used, and whereby the resistance of oil to emulsiication may be made satislfactory.

I am aware that it has been proposed to purify some oils, but not oils containing finely divided carbon, by substances or solutions that are stronglyv alkaline and which produce a precipitation of products of saponiication. However, such precipitates are in themselves partly soluble in the oil and an impurity is thereby introduced. And, as it is not practicable to separate them from the oil by centrifugal force,'par ticles of such products are left in the oil after centrifugal treatment and those particles carry 'into the oil such im urities as finely divided carbon. Entry o inelydivided carbon into the aqueous phase is hindered by the formation of a sludge layer composed of such precipitates and by hlgh specific gravity of the alkaline solution, particularly when such particles are not well freed of oil. In the practice of my process the aqueous reagent will be suiiciently dilute that water soluble impurities in the oil and 4products of saponification present or produced, and other products of any reaction between the reagent and the oil or its impurities, will all be in solution in the aqueous phase of the resulting mixture. Thus, after treatment of the oil in accordance with my invention with an aqueous reagent, the mlxture will include oil, that may be dried J and that may have its resistance to emulsification improved, and an aqueous phase containing impurities or products thereof that are in solution and a sediment com sed of dirt, metallic particles, carbon particles and any silica coming from the reagent. Grav- `ity settling of such a mixture will not produce between the oil and the aqueous phase a layer of sludge containing products of saponification as in processes heretofore suggested. It is because all impurities or products thereof, that are soluble, are in solution, that it is possible to effect a centrifugal separation of the aqueous phase and sediment from the oil.

While I have described my invention in detail and have referred to specific applications thereof I do'not intend that my invention shall be limited to such details or -to such specific applications but lintend that.

it shall be defined by the hereunto appended 2. The method of purifying impure oilthat contains finely divided carbon which comprises dispersing throughout the oil an aqueous alkaline reagent suiiiciently dilute that water soluble impurities and products of saponitication present will be in solution inthe a ueous phase of the resulting mixture, an separating the aqueous phase and impurities from the oil.

l3. The method of purifying impure oil that contains finely divided carbon which comprises dispersing throughout the oil an aqueous alkaline reagent suliiciently diluteA that water soluble impurities and products of saponiication present will be in solution in the aqueous hase of the resulting mixture, and centri ousnphase and impurities from the oil.

4. The method of urifying impure oil that contains finely dlivided carbon which comprises dispersing throughout the oil an aqueous alkaline rea ent su-iciently dilute" that water soluble impurities and ywater soluble products of any reaction produced by` the'reagent will be in solution in the aqueous phase of the resulting mixture, centrifugally separating the aqueous phase from the oil, and treating therecovered oil with adsorptive material. Y

5. -The method of urifying impure oil that contains finely ivided carbon which comprises dispersing throughout the oil an aqueous alkallne reagent suiciently dilute that water soluble impurities and water soluble products of any reaction produced by the reagent will be in solution in the 'aqueous phase of the resulting mixture, oentrifugall separating the aqueous phase from the oi and treating the recovered oil with not more than one percent of adsorptive material.

gally separating the aquethat contains finely divided carbon which comprises dispersing throughout the oil an aqueous alkaline reagent sufficiently dilute that water soluble impurities and water soluble products of any reaction produced by the reagent will be in solution in the aqueous phase of the resultingmixture, centrifugally separating the aqueous phase of the resulting mixture from the oil, agitating therecovered oil with not more than one ercent of adsorptive material, and separating the adsorptive material from the oil.

8. The method of purifyingimpure oil that contains nely divided carbon which comprises dispersing throughout the oil an aqueous alkaline reagent suficiently dilute that water soluble impurities and water sol- -uble products of any reaction produced by the reagent'will be in solution in the aqueous phase of the resulting mixture and containin a colloidal substance in suspension capa le of causing the carbon to lie within the .aqueous phase, and se arating the aqueous phase and impurities om the oil.

9. The method of purifying impure oil containing finely divided carbon which comprises dispersing throughout'the oil an aqueous alkaline reagent capable of being easily dispersed within the oil and having the property of facilitating the passage of carbonaceous impurities from the oil into the aqueous lphase of the resulting mixture and containing inl suspension a colloidal substance capable of causing the vcarbonrto lie within the aqueous phase, and separatmg the "aqueous phase from the o1l.

1o. The method of purifying .impure on containing finely divided carbonwhlch comprises dispersingl aqueous reagent aving a weak alkaline reaction capable of being easily dispersed within the oil and havin the property of facilitating the passage o carbonaceous impurities from the oil mto the aqueous phase of the resulting mixture, and separating the aqueous phase -from the oil.

11. The method of purifying impure oil containing finely divided carbon which comprises dispersing throughout the oil an aqueous mixture having a'weak alkaline reaction and havin the property when in contact with the o' of attracting toy it oppositely charged impurities of the oil, and separating from the oil impurities and the aqueous phase of the resulting mixture.

throughout the oil an rendered impure through use whichcomprises disl ersing ythroughout the oilan aqueous a kaline reagent sufliciently dilute .that water soluble impurities andwater soluble products of any reaction lproduced by the reagent will be in solution in the aqueous phase of the resulting mixture, and separatlng the aqueous phase from the oil.

14. The method of urifying impure oil that contains finely divided carbon which comprises dispersing throughout the oil an aqueous alkaline reagent sufiiciently dilute that Water soluble lmpurities andgwater soluble products of any reaction produced by the reagent will be in solution in the aqueous phase of the resultin mixture, separating the' aqueous phase o the resultin mixture from the oil, agitating the recovere oil with not more. than one percent of adsorptive material, and separating the adsorptive material from Ithe oil.`

. 15. The method of purifying impure oil that contains finely divided carbon which comprises'dispersing throughout the oil an aqueous alkaline reagent having an available alkalinity equivalent to the alkalinity of a solution containing 1/1% to 1% by Weight of caustic soda, and` separating impurities and the aqueous phase of the mixture from the oil.

16. Thel method of purifying impure oil that contains finely divided 'carbon which comprises dispersing throughout the oil an' aqueous alkaline reaent sufficiently dilute that. water soluble impurities and waterl solubleproducts of 'any reaction produced loidal compound in suspension and havingv an available alkalinity equivalent to the alkalinity of a solution containing 1/% to 1% by weight of caustic soda, and separating impurities and the aqueous phase of the mixture from the oil.

.18. In `a method for improving the-resistance of oil to emulsication the steps comprising first treating the oilwith an aqueous alkaline reagent containing a compound incolloidal suspension and thereafter agitating the oil with notmore than 1% of adsorptive material, and removing the adsorptive material from the oil'.

` 19. The method of purifying impure oil that contains finely divided carbon. which comprises dispersing throughout the oil an aqueous alkaline reagent having an avail-r able. alkalinity equivalent to the alkalinity of a solution containing 1&7@ by i'veight of caustic soda, and separating impurities and the aqueous phase of the mixture from the oil.

l20. The method of purifying impure oil which comprises dispersingf4 throughout the oil an aqueous solution containing 2% by weight of sodium silicate, and sepa-rating from the -011 impuritles and the aqueous phase of the resulting mixture.

2l. The method .ofk purify-ing impure oil.

20 which comprises dispersing throughout the 22. The method'of purifying impure'oil containing finely divided carbon Whlch comprises dispersing throughout the oil an aqueous reagent having a weak alkaline .r'eaction and having the property of dissolving al1 v products of saponifeation produced thereby and thereby rendering impurities including the iin-ely divided carbon separable .from the oil by centrifugal action, and centrifugally separating from the oil impui-ities and the aqueous' phase of the resulting mixture. A

In testimony whereof, I have Vsigned my name to this specification. 1

LEE H. CLARK. 

